The present invention concerns a method for differentiating between multiple noise jammer sources. More particularly, the present invention concerns a method for differentiating between multiple noise jamming sources in instances where two or more radar platforms are used to triangulate on the jamming sources for the purpose of ascertaining their precise locations.
Noise jammer discriminant measurements are difficult to make for several reasons. First, the wide bandwidth of the noise jammer signal transmissions proves difficult for the narrow bandwidth receivers required to operate with narrow beamwidth antennas. Further, the noise-like nature of the jammer transmissions is difficult to characterize in a receiver. Finally, even wide band jammer transmissions contain very little information. Such transmissions are similar to a spread spectrum signal where the entire spectrum must be received and demodulated to acquire any information.
When two or more surveillance radar platforms attempt to triangulate on multiple aircraft carrying noise jammers, the intersections of the noise strobes produce ghost positions which cannot be distinquished from actual aircraft positions. The problem is eased somewhat by geometric considerations but in the presence of numerous jammers, accurate position information (sufficient to vector interceptor aircraft) cannot be acquired.
Jammer noise "fingerprints" are very difficult to make. Therefore, it is desireable to have several measurements which can be used to better accommodate a wider variety of situations. In a related patent application by Carl D. Wise and Frank W. Hays, filed concurrently herewith, entitled Noise Jammer Discrimination By Noise Spectral Bandwidth, and having Ser. No. 618,288, a method is disclosed for estimating the noise spectral bandwidths of different jammers by measuring their respective duty cycles in a narrow band receiver. The present application describes a method for measuring amplitude and pulse width statistics to characterize the modulation differences in jammer signals.
It is therefore an object of the present invention to specify a method according to which it is possible to differentiate between multiple noise jammer sources having the same noise spectral bandwidth.
It is a further object of the present invention to provide a method for distinguishing between noise jammer sources having different noise modulation bandwidths.
It is another object of the present invention to provide a method for aiding in the location of multiple aircraft carrying narrow band noise jammer sources.